blender2ogre 0.5.8 export error - ReferenceError: StructRNA of type Mesh has been removed
It could perhaps help to update your version of the Orge3D exporter from 0.58 to 0.60 from  the bitbucket page. It seems the version you use (0.5.8) is written for blender 2.65 and the latest 0.6.0 version supports blender 2.66. Failing that I suggest taking steps to contact the guy who currently maintains the addon for advice.